1. Field of Invention
This invention generally relates to the production of Radio Frequency Identification Device (RFID) tags, specifically to the economical encoding and verification testing of finished UHF, HF and other frequency RFID Tags in a production environment.
2. Prior Art
RFID Tag Encoding
RFID chips, the basis of inlays, labels and tags, are typically designed with a plurality of memory elements. Some of said memory elements are changeable and others are not. The process of Commissioning new RFID Tags often involves reading the unchangeable fields from each new tag; saving the data from said unchangeable fields in a database; computing data to be written into said changeable fields; and writing said data. Commissioning operations typically take place inside a special purpose device like a label printer that also encodes RFID Tags, often called a Printer-Encoder. Commissioning operations are sometimes performed by larger scale singulated encoding processes on large printing presses, like the LineLogix system marketed by the current Inventor.
Commissioning operations are similarly sometimes performed by Bulk or Continuous Encoding operations on large printing presses. The Impinj company is the leader in technology that enables Bulk and Continuous encoding, specifically to UHFtags of Electronic Product Code (EPC) Class1 Generation 2 (Gen2). Their technology allows rapid encoding of large numbers of Tags; however, it has certain shortcomings that limit its usefulness. Overcoming those shortcomings is one subject of the current Invention. Extending the benefits of continuous encoding to RFID protocols that do not include such a mechanism, but which allow selection by Unique Identifier (UID), is another subject of the current Invention. Examples of such protocols are ISO15693 and ISO14443 High Frequency (HF) RFID Tags.
The shortcomings of the most common Continuous and Bulk Encoding technologies, which are overcome by the current Invention, include:                1. Lack of Ordering—because Continuous and Bulk Encoding operate on a plurality of tags, they cannot discern the order of said tags in their underlying medium, for example a moving paper web of tags or a conveyor bearing tagged items.        2. Incomplete Failure Data—Continuous and Bulk Encoding processes can report if a certain tag failed to complete an encoding process; however, those processes have no way to know whether any tags have escaped the process completely. For example, if a label or product bear a label with no RFID Tag, or if a good tag passes outside the effective range of the encoding mechanism, or if some weak tags slow the encoding mechanism such that good tags escape notice due to timing effects, the Continuous and Bulk Encoding mechanism will never report a failure.        3. Nondeterministic Failure Data—Continuous and Bulk Encoding processes may well report a failed encoding operation, or report a count of successful operations that disagrees with an external count of items moving through said process. But Continuous and Bulk Encoding processes will never be able to identify which of said items failed the Continuous and Bulk Encoding process. That fact requires any batch of such items to be separately tested, wasting time and resources. It will be shown that the present invention improves current Continuous and Bulk Encoding processes in all the above respects.        4. Specificity to Frequency Range and Protocol—The process of Continuous and Bulk encoding is part of the protocol definition of the EPC Class 1 Generation 2 RFID Tag for UHF. The techniques disclosed here allow the encoding of any RFID Tag in continuous motion, as long as the reader and protocol support selection by a Unique Identifier (UID).RFID Integrated Circuit Advances        
Ultra High Frequency (UHF) RFID Tags of Electronic Product Code (EPC) Class1 Generation 2 contain a memory bank known as the Tag Identifier (TID). In the original devices of this class, the TID was simply a short field bearing a manufacturer's code. Starting around 2010, devices of this class began to implement an optional extension to the TID—an unchangeable field bearing a large serialized number, typically 64 bits long. The value of each serialized TID on each RFID Tag so equipped is meant to be globally unique.
Much has been written on the usage of the TID for security purposes. The current invention uses the TID in an elegant yet unobvious manner to improve common Continuous and Bulk Encoding processes by providing data related to the order of items entering said processes.
The current invention further uses the Unique Identifier (UID) of some RFID Tags to support encoding of those tags in continuous motion. High Frequency (HF) RFID Tags do not have a Bulk or Continuous Encoding capability, but do support selection by UID. It is possible to extend the benefits of this Invention to tags in the HF and other frequency ranges by using multiple individual encoders, each programmed to look for a particular UID, and to encode unique corresponding data to said RFID Tag. In obvious implementations, the long time needed to encode RFID Tags far overshadows the short time needed to read them. An obvious process for continuous encoding of HF Tags would have to run slowly enough that each tag was coupled to the encoding antenna for the worst case encoding time; however, that is not practical because it would slow the continuous process to an uneconomical degree. Further, an obvious process would have to restrict the size of the encoding antennas so that one and only one Tag was coupled to each antenna at any time, further driving the speed of the process down to uneconomical levels. The current Invention discloses an elegant but unobvious mechanism for overcoming these described limitations and encoding HF RFID Tags, indeed any RFID Tag that supports selection by UID, in a continuous process at economic speeds.
3. Objects and Advantages
Accordingly, several objects and advantages of this Apparatus and Method for Serialized Continuous Encoding of RFID Tags are the encoding of RFID Tags in continuous motion at the best speeds attainable by common Continuous, Bulk and Selected Encoding processes while further:
(a) Determining the order of items entering the process
(b) Detecting failures via a plurality of mechanisms
(c) Isolating or marking failures without a separate test process
(d) Reporting on the sequence of items in a batch of said items, including the position of each specific item in the batch, and its success or failure in the Encoding process.
Further objects and advantages will become apparent from a consideration of the ensuing description and drawings.